The present invention relates to a fuse circuit, provided in a semiconductor integrated circuit (hereinafter abbreviated to an LSI) and having a wiring pattern and a fuse connected between the wiring patter and a pad, for setting a signal on the pad in a fused status of the fuse.
FIGS. 2(a) and 2(b) are views each showing a configuration of a principal portion of a conventional fuse circuit. FIG. 2(a) is a plan view of the fuse circuit. FIG. 2(b) is a view showing a circuit in FIG. 2(a).
This fuse circuit is formed on the LSI, and includes two pads 1, 2, a wiring pattern 3 and a fuse 4. The wiring pattern 3 constitutes, e.g., a ground line or a power supply line. Connected to this wiring pattern 3 are the pad 1 and one end of the fuse 4. The other end of the fuse 4 is connected to the pad 2.
In the fuse circuit shown in FIG. 2, in a state where the fuse 4 is not fused, a ground potential GND or a power supply potential Vcc given via the fuse 4 and the pad 2 as well is supplied to an unillustrated flip-flop connected to the pad 2. If the flip-flop connected to the pad 2 is not supplied with the ground potential GND or the power supply potential Vcc via the pad 2, a voltage is applied between the pad 1 and the pad 2. The fuse 4 is fused upon applying the voltage. When the fuse 4 is fused, the flip-flop is supplied with the power supply potential Vcc or the ground potential GND, logic data opposite to the case where the fuse 4 is not fused, is outputted.
There arises, however, the following problem inherent in the prior art fuse circuit.
The prior art fuse circuit has no alternative but to determine whether to disconnect one pad 2 of the LSI from the wiring pattern 3 or to introduce the signal from the wiring pattern directly into the flip-flop via the pad 2, depending on whether the fuse 4 should be fused or not. Namely, it is unfeasible to make the signal flow to the flip-flop via the pad 2 by selecting a plurality of signals. Actualization of this involves preparing a mask pattern for forming a wiring pattern different from the on shown in FIG. 2, and forming a new wiring pattern different from the one in FIG. 2 by use of the mask pattern. Therefore, development of the product is time-consuming, and there is no effect in terms of a mass-production of the LSIs.